1. Field of the Invention
The present invention relates to a light-emitting element controller, an optical transmitting apparatus, and a method and a program for determining a driving current, and more specifically, to a light-emitting element controller which controls a semiconductor light-emitting element, an optical transmitting apparatus, and a method and a program for determining a driving current.
2. Description of the Related Art
In optical communication, semiconductor lasers are typically used as light-emitting elements. The semiconductor laser has current-optical output characteristics that it emits light when its driving current exceeds a current value called an oscillation threshold current (hereafter, called “threshold current”), and the optical output is proportional to the amount of the driving current exceeding the threshold current.
The semiconductor laser is driven by a driving current made by superimposing a bias current and a pulse current one upon the other, and drive conditions thereof are appropriately set based on the current-optical output characteristics.
By the way, the current-optical output characteristics vary with its environmental temperature change and aging.
Therefore, to cope with a change in the current-optical output characteristics, it has been tried to change the drive conditions (the bias current and the pulse current) of the semiconductor laser (for example, Japanese Patent Laid-Open No. Hei 7-147446).